1. Field of the Invention
This invention relates to bearings for use in steering assemblies and, more particularly, to a bearing assembly that can be press fit onto a steering shaft and/or within a shaft housing without excessive stress on the bearing races and without significant impact on steering torque while also tolerating angular misalignment between the shaft and housing.
2. Disclosure of Related Art
In a conventional steering assembly for a vehicle or other device, a steering wheel or other steering input member is connected through a steering shaft (i.e., the steering column) to a steering gear or similar component used to transmit motion from the input member to one or more steered wheels. The steering shaft is supported within a housing for relative rotation by bearing assemblies. For proper functioning of the steering assembly, the clearances between (i) the bearing assembly and the shaft and/or (ii) the bearing assembly and the housing are relatively small. A variety of bearing assemblies have been developed for use in steering assemblies, but each of these conventional bearing assemblies has one or more significant deficiencies.
One conventional bearing assembly used in steering applications includes a pair of opposed spring preloaded angular contact bearings. In this type of bearing assembly, means, such as a wedge, are provided to remove clearance between either the steering shaft and the inner race of the bearing or the shaft housing and the outer race of the bearing. In addition to requiring the wedge, this type of bearing assembly is difficult to use in steering applications because the tolerances in steering applications result in significant variation in spring compression and, therefore, bearing preload ultimately impacting system stiffness and torque requirements. This type of bearing assembly also has difficulty accommodating angular misalignment in the system and generates a fair amount of acoustic noise due to relative motion between the bearing elements, preload components and the steering shaft and housing.
Another conventional bearing assembly used in steering applications is an elastomer preloaded ball bearing in which an elastomeric material acts as a spring on a split inner race or a split outer race to preload the ball bearings and the bearing races. Because of the difficulty in maintaining the position of the split race, this type of bearing assembly is unable to handle significant loads. The assembly also has significant torque requirements because significant preloads are required to maintain proper stiffness for steering applications and the required torque can also vary.
Yet another conventional bearing assembly used in steering applications is an elastomer preloaded needle bearing in which an elastomeric material acts on a split or deformed outer race to preload the needle bearings and bearing races. Again, the difficulty in maintaining the position of the split race and variations in load on the deformed race make the assembly unsuitable for relatively large loads. Further, the assembly has significant torque requirements because of the significant preloads required to maintain proper stiffness for steering applications.
Another conventional bearing assembly sometimes used in steering applications includes precision ground ball bearings such as ground race ball bearings. This type of bearing assembly is very sensitive to misalignment, however, which can result in relatively high and variable torque requirements and premature bearing failure. As a result, precision ball bearings generally cannot be used in steering applications.
Conventional bearing assemblies are typically press-fit onto the steering shaft and/or shaft housing. The races in each of the above-described bearing assemblies are subject to damage when press-fit. To reduce the risk of damage, steering systems have been modified to reduce tolerances in the system and/or adapters have been required to absorb pressure from the press-fit. In addition, the press-fit relationship creates specific problems for certain types of bearing assemblies. Precision bearings, for example, typically cannot be used because they are more likely to suffer damage or to be impacted by a reduction in clearance than other bearings. Preloaded bearings suffer from changes to the preload caused by the press-fit effecting stiffness and rotational torque requirements.
The inventors herein have recognized a need for a bearing assembly that will minimize and/or eliminate one or more of the above-identified deficiencies.